(a) Field of the Invention
The present invention concerns a pickup cartridge for picking up a signal recorded on a record disc, and more particularly it pertains to a pickup cartridge of the moving magnet type.
(B) Description of the Prior Art
A pickup cartridge of the moving magnet type, in general, is constructed so that an armature magnet is arranged between pole pieces which constitute a part of a closed magnetic path containing this magnet and that the magnet is supported so as to be able to move or vibrate jointly with a cantilever.
In a known pickup cartridge of the aforesaid type, it has been usual to arrange so that a magnet which is secured to a cantilever is formed into a disc or a columnar shape; that the cantilever and the magnet which are thus integral with each other are supported between pole pieces via an elastic damping member; and that the cantilever is pulled by a suspension wire such as piano string to suppress the tendency of this cantilever of making a longitudinal displacement. In such an arrangement of the prior art, the center of vibration of the vibrating system containing the cantilever, the armature magnet, the damping member and the suspension wire tends to move depending on the amplitude of vibration of the vibrating system. Furthermore, the distance between the pole pieces and the magnet tends to vary depending on the amplitude of vibration of the vibrating system. Accordingly, the pickup cartridge having the aforesaid arrangement is not able to faithfully pick up the signal recorded on a record disc without causing distortion of the signal. Moreover, owing to the fact that the distance between the pole pieces and the armature magnet can vary depending on the armature magnet of the vibration amplitude of the vibrating system, it is not possible to arrange the pole pieces so as to face the armature magnet at positions sufficiently close thereto. Thus, the pickup cartridge having such an arrangement as described above is not able to pick up the recorded signal of the record disc with good sensitivity.